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2010 KTM 530 popping and backfire

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My newly purchased 530 pops and backfires once in a while on deceleration. I assume this is normal. My bike has a JD jetting kit and the muffler has been uncorked. I have 15.3 hours on it and am concerned about valve adjustment. Should I stop riding until I set valves? Always had 2 strokes until now so have never set valves. I would like to wait until it snows but don't want to damage the engine riding in the mean time. I went 99 KM on fuel then had to switch to reserve. Don't know yet how far reserve will take me. I have 51 tooth rear and 14 tooth front. When I switch to the mortar set up I may try 48 rear and 15 front so I can use the same chain. Also have 45 tooth rear but will have to change the chain to use and that sounds like a pain in the ass. Love the bike so far but concerned about valve adjustment.

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Checking the valve clearance is easy on this motor. Worthwhile to pick up a CD service manual as they are very inexpensive. This link is also very helpful;

http://paochow.com/forum/index.php?topic=40.0

You may have an exhaust airleak or check your jetting specs. Fuel screw may need to be backed out a bit if your temps have recently dropped. Mine does not pop or backfire at all.

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My guess would be the fuel screw, too. Back it out a 1/4 turn and I'm thinking that the popping will go away.

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I have the same issue with backfiring. My jetting (with JD jet kit) seems spot on as far as performance and response. Fuel screw is already backed out 1.75 turns which is where it idles and runs best. Is there an effective way of determining if the popping on decel is due to a lean jet condition or an exhaust leak (presumably at the header)?

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I've heard that they all come lean and should be rejetted. From what I've read the JD kit is an expensive waste if you can figure out which jets you need for your area (altitude); the jets are cheap.

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make sure your o-ring is on the fuel screw.

The JD Kit is worth the money IMO because you get Needles, jets, and a good instruction on where a baseline might be.

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My 525 was popping pretty badly. I sealed the exhaust and installed a JD kit but it still popped.

I adjusted the valves and it all but went away. I'm not sure if you can completely eliminate the popping but mine only does it on rare occasions now. Before, it was so bad I had to pull the clutch and coast to a stop because the popping was so bad, it was embarrassing.

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Further questioning the group, my 2003 450 MXC has begun to pop and backfire on deacceleration just recently, in conjunction with carb issues (clogged jets, I think) Will clogged jets cause backfiring? (A rookie question I know, but I am hoping to avoid messing with the valves.) Thanks in advance.

Edited by logger73
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Further questioning the group, my 2003 450 MXC has begun to pop and backfire on deacceleration just recently, in conjunction with carb issues (clogged jets, I think) Will clogged jets cause backfiring? (A rookie question I know, but I am hoping to avoid messing with the valves.) Thanks in advance.

How are the temps where you are? Has it been getting cooler? Has the bike sat for any length of time?

If it has been getting cooler you might just need to adjust your fuel screw to richen the mixture under decel at closed throttle. Where are you noticing the "clogged jet" feel? 1/4 throttle, 1/2-3/4 throttle? If it is when you are accelerating, and the temps have changed, you might need a needle or position change.

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How are the temps where you are? Has it been getting cooler? Has the bike sat for any length of time?

If it has been getting cooler you might just need to adjust your fuel screw to richen the mixture under decel at closed throttle. Where are you noticing the "clogged jet" feel? 1/4 throttle, 1/2-3/4 throttle? If it is when you are accelerating, and the temps have changed, you might need a needle or position change.

The bike had sat for about 3 Mos and it has gotten colder here, though nothing below 30 degrees.

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I had similar symptoms with my 530 at one point. I don't remember the exact settings but my bike now has a needle from a 560smr and a couple other changes. Works better then any other system out there imo. I've ridden bikes with the JD kit and in comparison the JD kitted bikes feel lacking. They run right at one small portion of the throttle and then kinda suck everywhere else. My bike runs great from sea level 8k feet so far no pops anywhere. The popping is a sign of being lean or an air leak. MY guess is the bike is still lean somewhere.

Hopefully this helps you.

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